How Cation Substitutions Affect the Oxygen Reduction Reaction on La_2−xSr_xNi_1−yFe_yO₄

Abstract

The atomic proximity of two disparate structural motifs in interleaved structures such as that adopted by La2NiO4, which alternates rock salt and perovskite motifs, offers potential synergistic effects and increased tunability for electrocatalyst behavior. Structural and voltammetric analysis of the intersecting composition series LaSrNi1−yFeyO4+δ and La2−xSrxNi0.7Fe0.3O4+δ show that tuning different cation sites uniquely affects structure and behavior. Correlations between X‐ray diffraction and Raman spectroscopy results reveal that structural changes in the a‐b plane are uniformly matched by the c‐axis following La−Sr exchange, while Ni−Fe exchange distorts the structure by expanding the crystal c‐axis and generating oxygen defects with a distinct signature in Raman spectra. Correlations between rotating ring‐disk electrode voltammetry results and structural parameters show that only Fe substitution has a direct effect on the electrocatalytic oxygen reduction reaction. We link systematic changes observed for onset of electrocatalytic oxygen reduction reaction, Tafel slope, and selectivity to distortions in the B‐site environments. This analysis demonstrates that correlational analysis linking electrochemical behavior parameters to multiple structural characterization techniques is an effective means to probe the effect of individual compositional substitution on electrocatalytic behavior.

Electro-Oxidation Reaction of Methanol over La2–xSrxNi1–y(Mn/Fe/Co)yO4+δ Ruddlesden–Popper Oxides

“…The structural information and phase purity of the solution combustion-synthesized La 1.4 Sr 0.6 Ni 0.9 (Mn/Fe/Co) 0.1 O 4+δ was probed by powder XRD. The representative XRD patterns as shown in Figure a indicate that the synthesized materials crystallized in the phase-pure Ruddlesden–Popper structure and are in good agreement with the reported profiles. ,,− La 1.4 Sr 0.6 Ni 0.9 (Mn/Fe/Co) 0.1 O 4+δ exhibited a tetragonal symmetry with the I 4/ mmm space group [JCPDS No. 81-0742].…”

“…Among all the Ni-based metal oxides, layered Ruddlesden–Popper perovskite oxides, such as La 2 NiO 4+δ with a K 2 NiF 4 structure, exhibit notable potential as catalysts for MOR. , La 2 NiO 4+δ possesses a characteristic arrangement, where LaNiO 3 perovskite layers containing corner-sharing NiO 6 octahedra are combined with alternating LaO rock-salt layers along the c -axis. This configuration creates a relatively open structural framework surface that allows oxygen-exchange properties where oxygen from the perovskite layer can occupy interstitial sites of the rock-salt layer and diffuse laterally. ,− Throughout the process of incorporating interstitial oxygen atoms, the host structure supplies electrons to the surface oxygen, while creating holes in the valence band. The presence of interstitial oxygen and holes has a significant impact on determining comprehensive electrochemical properties.…”

Interfacial and Electronic Modulation of W Bridging Heterostructure Between WS2 and Cobalt‐Based Compounds for Efficient Overall Water Splitting

“…In addition, the P─O groups in the catalysts can also enhance the catalytic activity, as the phosphate groups could induce a distorted local geometry that favor for the adsorption of water and can also serve as proton acceptors to promote the oxidation of metal atoms. [65] Similarly, the peak intensities of the S 2p 1/2 and S 2p 3/2 orbitals are also significantly weakened accompanied by the enlargement of the S─O bonds (Figure 5f), while revealing the conversion of metal sulfides to metal oxides or hydroxides during the catalytic process. [66] The XPS data of WS 2 @W-CoO x and WS 2 @W-CoC x after the HER and OER reactions are shown in Figures S19 and S20, Supporting Information.…”

Tuning the Oxygen Reduction Reactivity of Layered Perovskites Using the Jahn–Teller Effect

“…Layered perovskite oxides of the A 2 BX 4 type offer an intriguing ability to interface structural regions with redox activity to regions that are dominated by ionic bonding. This combination introduces properties that have been shown to introduce properties such as oxide conductivity, , superconductivity, , magnetism, and catalysis. ,,− The diversity of properties that can be installed into this family of materials has led to the identification of many examples, including La 2– x A x CoO 4 (A = Sm 3+ , Gd 3+ , Dy 3+ ), Nd 2– x Sr x Ni 1– y Co y O4, La 2 Co 1– y Cu y O 4 , La 2 Ni 1– y Co y O 4 , and La 2– x Sr x Ni 1– y Co y O 4 . Their electrochemical behavior, however, has been understudied compared to their classic perovskite analogues, and we find no previous reports on the ability of La 2– x Sr x Ni 1– y Co y O 4 to catalyze ORR.…”

“…Such behavior demonstrates a complex electronic structure in this family of materials, where variable oxidation states, ionic defects, and spin states combine to yield the observed electronic structure and properties. Electrocatalysis shows distinctive sensitivity to the type and concentration of defects in solid state materials, as seen by the demonstration that B-site substitution alters the electronic structure of La 2– x Sr x Ni 1– y Fe y O 4 to facilitate the electrocatalytic oxygen reduction reaction (ORR), but that tuning oxygen vacancies by A-site doping is required to drive electrocatalytic CO 2 reduction on La 2– x Sr x CuO 4 . ,, We therefore analyze the ORR capabilities of a subset of La 2– x Sr x Ni 1– y Co y O 4 to gain insight into how structure and reactivity correlate in this family of materials.…”